CPM (Converged IP Messaging) was proposed by Open Mobile Architecture (OMA) in 2005, with the purpose of realizing the interworking of various message services, providing unified message services and perfect, unanimous and convenient message service experience. CPM converges various existing message services including Instant Message (IM), Push-To-Talk over Cellular (POC), Mobile E-mail (MEM), Short Messaging Service (SMS), Multimedia Messaging Service (MMS), and so on.
At present, CPM V1.0 specification is being enacted by OMA. The forms of CPM include: CPM message based on pager-mode, large message Mode CPM Message based on session-mode, other CPM session service based on session. Users need to register and login the CPM system—in other words, to be online—before using these services.
The pager-mode message is transmitted by Session Initiation Protocol (SIP) message between the CPM Clients of receiver and sender and the CPM system. If the size of message exceeds a threshold (e.g. 1300 bytes), the SIP message could not be used for carrying the pager-mode message when the sender need to send a large message mode CPM.
The CPM system has defined several main logical function entities: CPM Client, Participating Function (PF) entity, Controlling Function (CF) entity, Message Storage Server, Content Storage Server, Interworking Selection Function entity, Interworking Function entity, and so on.
The CPM system identifies a user uniquely with CPM address, according to architecture design idea of the CPM system, the CPM address belongs to different CPM participating function entities in terms of belonging relationship, the network environment where the participating function entity is located (including the SIP/IP core network where said participating function entity is located) is also called the home domain of the user to which the participating function entity belongs, on the basis of this idea, the above-mentioned several main services of CPM are controlled in signaling plane based on SIP protocol, therefore the signaling plane is through the participating function entities. For example, any CPM signaling sent out by a CPM client will be routed to the participating function entity to which the sender belongs—i.e. originating participating function entity—by the SIP/IP core network according to the address of the sender after coming into the CPM network environment, and be routed to the participating function entity to which the receiver belongs—i.e. destination end participating function entity—according to the address of the receiver. That is to say, the signaling call is initiated at the originating participating function entity and terminated at the destination end participating function in the environment of CPM system.
When a CPM user initiates a call to a group (e.g. sends a large message mode CPM message to a group, or initiates a conference call to a group), the signaling will be routed to a controlling function entity by the SIP/IP core network in terms of group address, the service controlling related to the group is performed by the controlling function entity, after the signaling plane reaches the originating participating function entity.
When the CPM system and non-CPM system interwork, the signaling will be routed to the interworking selection function entity by the SIP/IP core network finally, and the final interworking function entity will be selected by the interworking selection function entity.
In prior art, there is not a complete solution for sending large message mode CPMC message to a non-CPM system user. The CPM system user sends a large message invite message to a user that does not sign the CPM service, when the signal arrives at the originating function entity, the originating participating function entity sends the invite message to the interworking selection function entity according to some routing strategy since the destination end is not a CPM system user, that is to say, the interworking with the non-CPM system is triggered at the originating participating function entity.